Real 3D microsphere lasers by femtosecond laser processing

In this article, we have mainly demonstrated the fabrication of a dye-doped polymer whispering gallery mode (WGM) microsphere by femtosecond laser two-photon polymerization, which shows good surface smoothness with a fabrication spatial resolution beyond the diffraction limit. The microcavity shows excellent lasing performance with a quality factor of similar to 3000. We have found that the lasing behavior of the 3D microlaser depends strongly on the diameter of the microsphere, that is, the lasing output changes from multimode to single mode gradually with the shift of laser wavelength when the diameter of the fabricated microsphere decreases. Our results can provide an easier solution for fabricating 3D single-mode microlasers with controlled resonance wavelength.